Consider a dataset about people. There is a unary relation person and a binary relation likes. person(x) is true if and only if x is a person, and likes(x,y) is true if and only if x likes y. See example below.

Write an expression that evaluates to a list of people in descending order of popularity. (One person is more popular than another if he or she is liked by more people.) For example, given the dataset above, the expression should evaluate to [c,b,a].

Although the concept is simple, the expression is likely to be a little complicated. The goal of this assignment is to give you exercise in writing safe functional expressions on lists and numbers with aggregate operators and predefined vocabulary.